JPS62119020A - Metering device for injection molding machine - Google Patents

Abstract

PURPOSE:To increase the metering accuracy by a method wherein the retreating position of a screw in metering is detected by a detecting means for he position of a servomotor to reduce the rotation of the screw when the position of the screw has arrived at a speed- reducing position and to stop it at a set metering point. CONSTITUTION:A metering point and the position of reducing the speed of a screw in accordance with the inertia of a driving mechanism or the like generated by the revolving speed of the screw are set and memorized in a memory means D and when a motor A is rotated to start metering, the screw is retreated by the pressure of molten resin against a black pressure applied by another motor B. The retreating position of the motor B is detected by a detecting means C and the metering point as well as a speed reducing point, memorized in the memory means D, are compared in the detecting means E and the detecting means F. When the position of the screw has arrived at the speed-reducing point, a detecting output is outputted from the detecting means F and a control means G reduces the speed of the motor A to revolve the screw at a low speed. Subsequently, when the detecting means E detects that the screw has arrived at the metering point, the control means G stops the motor A. According to this method, the setting of the metering point can be facilitated and the metering may be effected correctly without being affected by the inertia of a screw revolving mechanism.

Description

[Detailed description of the invention] Industrial applications The present invention relates to fft and ffl necking for injection molding machines.

In particular, the present invention relates to an injection molding machine in which a motor is used as a drive source for rotating a screw, and a servo motor is used as a drive source for an injection mechanism to apply back pressure during metering.

Conventional technology In conventional injection molding machines, the screw is rotated by a motor or the like during metering, and back pressure is applied by hydraulic screws, etc., the screw retreats, and when the metering point is reached, this is applied by a limit switch, etc. was detected and the rotation of the screw was stopped. However, even when the screw reaches the weighing point and the limit switch is activated, the screw rotates and does not stop due to the inertia of the screw rotation mechanism, and as a result, the total amount of rotation is too large, or the weighing point is not adjusted in consideration of inertia. If the limit switch was placed in a slightly forward position, the measurement would be insufficient, and highly accurate measurement could not be achieved due to the limit switch installation position error and operation error. This measurement error causes short shots, sink marks, and burrs, making it difficult to obtain products of good quality. Therefore, a method is known from Japanese Patent Publication No. 52-43869 in which the screw rotation is reduced at a position slightly before the measuring point to reduce the inertia and the screw is stopped at the measuring point, but this method also Since this method uses a limit switch to detect the limit switch, measurement errors occur due to limit switch installation position errors and operational errors.Also, the inertia of the screw rotation mechanism etc. interacts with the rotation speed of the screw, so the limit There is a drawback that highly accurate measurement cannot be obtained unless the setting position of the switch is moved every time the screw rotation speed is varied.

Problems to be Solved by the Invention The present invention improves the above-mentioned drawbacks of the prior art.It is easy to set the measuring point, and even if the screw rotation speed at the final stage during metering is different, the screw rotation mechanism can be used. The object of the present invention is to provide a measuring device for an injection molding machine that can accurately measure without being affected by the inertia of the injection molding machine.

Means for solving the problem Figure 1 shows 1. This is a block diagram of the means adopted by the present invention to solve the above problems, in which a screw for metering is rotated by a screw rotation motor A, and an injection servo motor B is used to drive an injection mechanism that moves the screw in the axial direction. In an injection molding machine that applies constant back pressure,
a position detecting means C for detecting the position of the screw from the position detector of the injection servo motor B; a memory means storing at least the screw position of the measuring point where metering ends; and a screw position detected by the position detecting means C. A measuring point detecting means E detects the measuring point position of the screw by comparing the position with the measuring point stored in the above storage means, and a measuring point detecting means E detects the screw measuring point position detected by the position detecting means and the measuring point set slightly before the above measuring point. A screw deceleration point detection means F compares the deceleration screw positions and detects the deceleration start position, and the measurement point detection means E sets the rotation of the screw rotation motor to a very slow speed based on the detection output of the screw deceleration point detection means F.
The above-mentioned problem was solved by providing a rotation control means G for stopping the driving of the screw rotation motor based on the detected output.

Function: The above-mentioned memory means is configured to set and store the deceleration screw position slightly before the measuring point, at least in accordance with the inertia of the drive a of the screw caused by the rotational speed of the final stage screw at the measuring point and at the time of measuring. Then, when the screw rotation motor A is rotated to start metering, the screw retreats against the back pressure applied by the injection servo motor B due to the pressure caused by the melting of the resin. The retracted position of the screw is detected by position detection means C such as a position detector provided on injection servo motor B, and is detected by position detection means C by measuring point detection means E and screw deceleration point detection means F. The position is compared with the measuring point and screw deceleration point stored in the storage means, and when the screw position reaches the screw deceleration point, a detection output is output from the screw deceleration point detection means and the rotation control means G controls the screw rotation motor. A
Reduce the rotation speed of the screw to avoid rotating it at a low speed.

Subsequently, when the measuring point detecting means E detects that the screw has reached the measuring point, the rotation controlling means Q stops driving the screw rotation motor and ends the measuring.

Embodiment FIG. 2 is a block diagram of main parts of an embodiment of the present invention, in which 1 indicates a control device such as a numerical control device for controlling an injection molding machine;
2 is a microcomputer (hereinafter referred to as CPU); 3 is a ROM that stores control programs for controlling each operation of the injection molding machine such as weighing, injection, mold clamping, etc.; and a RAM that is used for temporary storage of data, etc., which will be described later. Memorizes various setting values such as the screw rotation speed of each stage during metering, the switching screw position of each stage, the metering point that indicates the screw position at which metering ends, and the screw deceleration point that decelerates the screw rotation before the metering point. 4 is a manual input device for inputting various setting values and various commands; 5 is a screw rotation axis control circuit such as a servo circuit that drives and controls the servo motor M1 that rotates the screw; 6
is an injection shaft control circuit such as a servo circuit that drives and controls the injection servo motor M2 that drives the screw in the axial direction to perform injection and provides back pressure during metering, and Pi and r'2 are the servo motors M1. A position detector such as a pulse encoder provided at M2; 7 a counter for reversible counting in response to pulses from the position detector P2 of the injection motor M2;
8 is a bus.

Figure 3 (B) is a diagram showing an example of the operation during measurement in this embodiment. Figure 3 shows an example of the operation during measurement when the screw is not decelerated and rotated at a position slightly before the set measurement point. Therefore, this example shows an example in which the rotational speed of three stages of screws is changed during metering.

First, to explain the conventional example, metering is started, the screw rotates at the set speed N1, and the screw position is S.
When the screw moves back to Pl, it switches to the second stage rotation speed N2, then when the screw position moves back to SF3, it switches to the final stage rotation speed N3, and when the screw moves back to the set weighing point 5GBK position, the screw rotation motor stops. However, as shown in Figure 3 (a), even if the motor for rotating the screw is stopped, the screw rotation still continues. 1
The screw rotates due to the inertia of the Jta structure, etc., and as a result, the screw moves backward and stops at a retreated position exceeding the set measuring point 5CBK, resulting in an increase in metering. Furthermore, even if the set measuring point 5CBK is set with this inertia in mind, the inertial force will fluctuate due to changes in the final stage screw rotation speed, and the screw retraction will change. Furthermore, the inertia force must be determined for each individual injection molding machine, which is inconvenient and prevents highly accurate measurement.

Therefore, as shown in FIG. 3 (0), the screw rotation speed is reduced from the screw retraction position at a distance 1 before the set metering point 5CBK in the final stage, so that the inertia of the screw rotation mechanism can be ignored. By doing this, highly accurate measurement can be performed.The operation will be explained below along with the operational processing flow of this embodiment shown in FIG.

When weighing is started, the CPLJ 2 reads the first stage screw rotation speed N1 set in the memory 3, and drives the servo motor M1 via the screw rotation axis control circuit 5 to rotate the screw at the rotation speed N1. As a result, when the screw retreats, the position of the injection servo motor M2 is detected r.
Counter 7 counts pulses from AP 2, detects screw position 11 fffisP, and when the screw position SP comes to the switching point SPI from the 1st stage to the 2nd stage set and stored in the memory 3, the 2nd stage The screw rotation speed N2 is read from the memory, and the screw is rotated at this rotation speed.

Thereafter, the weighing Wh operation is performed in the same manner (step 81).

When the final stage is reached, the CPIJ 2 determines whether the screw position SP has changed to a screw deceleration position that is slightly before the weighing point 5CBK set and stored in the memory 3 (one sentence before the screw position). Step 82>. Depending on the type of injection molding machine, the position at which the rotation of the screw is decelerated may be programmed and fixed as a position a certain distance before the weighing point 5GBK. For injection molding machines of the type that can greatly change the screw rotation speed (N3),
This deceleration distance statement is also set from the manual input device 4 and the memory 3
In step S2, this distance statement may be read out, and the distance statement may be decreased or stopped from the set measuring point 5CBK and compared with the screw position f:lsP. In this way, the deceleration position a (SCBK-Jl
), the CPU 2 drives the screw with slow rotation n (step S3), determines whether the screw position SP has reached the weighing point 5CBK (step S4), and when it reaches it, stops the screw rotation. It is stopped (step S5), and the weighing process is completed.

Effects of the Invention As described above, the present invention detects the retracted position of the screw during metering using a position detection means such as a position detector of an injection servo motor that drives the screw in the axial direction, and the screw position is detected at the set metering point. When a slightly earlier deceleration position is reached, the screw rotation is reduced to a low speed and stopped at the set measurement point, making it possible to perform highly accurate measurement without being affected by the inertia of the screw rotation mechanism. In addition, the position of the screw is detected by a position detector installed on the servo motor for injection, and no limit switch is used, so the installation of a limit switch requires only 1ffl.
Accurate measurement is possible without being affected by l differences or operational errors. Furthermore, it is possible to easily change the settings of the weighing point and deceleration point, and the position of the deceleration point can also be easily changed according to the final stage screw rotation speed during weighing, resulting in optimal weighing. can be processed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the means adopted to solve the problems of the prior art according to the present invention, FIG. 2 is a block diagram of the main part of an embodiment of the present invention, and FIG. The operation explanatory diagram, FIG.
--1-. 1...Control device. Ml, M2...Servo motor, P
l, P2...Position detector.

Claims (2)

[Claims] (1) In an injection molding machine in which a screw is rotated by a screw rotation motor during metering, and a constant back pressure is applied by an injection servo motor for driving an injection mechanism that moves the screw in the axial direction, the injection servo motor a position detection means for detecting the position of the screw from a position detector of the motor; a storage means for storing at least the screw position of the measuring point where the measurement ends; and a screw position detected by the position detection means and the screw position recorded in the storage means A measuring point detecting means detects the measuring point position of the screw by comparing the measured measuring points, and a measuring point detecting means detects the measuring point position of the screw by comparing the screw position detected by the position detecting means and a deceleration screw position set slightly before the measuring point and determines the deceleration start position. Screw deceleration point detection means to detect, and rotation control that causes the screw rotation motor to rotate at a slow speed based on the detection output of the screw deceleration point detection means and stops driving the screw rotation motor based on the detection output of the measurement point detection means. A measuring device for an injection molding machine, characterized in that it has a means. (2) A deceleration section distance is set and stored in the storage means, and the screw deceleration point detection means detects a value obtained by subtracting the deceleration section distance from the weighing point stored in the storage means using the position detection means. A measuring device for an injection molding machine according to claim 1, which detects and outputs a screw deceleration position by comparing the determined screw positions.